// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_POWER_MONITOR_POWER_MONITOR_SOURCE_H_
#define BASE_POWER_MONITOR_POWER_MONITOR_SOURCE_H_

#include "base/base_export.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/observer_list_threadsafe.h"
#include "base/synchronization/lock.h"

namespace base {

class PowerMonitor;

// Communicates power state changes to the power monitor.
class BASE_EXPORT PowerMonitorSource {
public:
    PowerMonitorSource();
    virtual ~PowerMonitorSource();

    // Normalized list of power events.
    enum PowerEvent {
        POWER_STATE_EVENT, // The Power status of the system has changed.
        SUSPEND_EVENT, // The system is being suspended.
        RESUME_EVENT // The system is being resumed.
    };

    // Is the computer currently on battery power. Can be called on any thread.
    bool IsOnBatteryPower();

protected:
    friend class PowerMonitorTest;

    // Friend function that is allowed to access the protected ProcessPowerEvent.
    friend void ProcessPowerEventHelper(PowerEvent);

    // Get the process-wide PowerMonitorSource (if not present, returns NULL).
    static PowerMonitorSource* Get();

    // ProcessPowerEvent should only be called from a single thread, most likely
    // the UI thread or, in child processes, the IO thread.
    static void ProcessPowerEvent(PowerEvent event_id);

    // Platform-specific method to check whether the system is currently
    // running on battery power.  Returns true if running on batteries,
    // false otherwise.
    virtual bool IsOnBatteryPowerImpl() = 0;

private:
    bool on_battery_power_;
    bool suspended_;

    // This lock guards access to on_battery_power_, to ensure that
    // IsOnBatteryPower can be called from any thread.
    Lock battery_lock_;

    DISALLOW_COPY_AND_ASSIGN(PowerMonitorSource);
};

} // namespace base

#endif // BASE_POWER_MONITOR_POWER_MONITOR_SOURCE_H_
